Commons Lang、Validate.notEmpty()

import java.util.*;
import org.apache.commons.lang.Validate;

public class C2009051800 {
    public static void main(String[] args) {
        Map m = new HashMap();
        m.put("foo", 1);

        Validate.notEmpty(m);

        m = new HashMap();
        Validate.notEmpty(m);
    }
}

で、

Exception in thread "main" java.lang.IllegalArgumentException: The validated map is empty
        at org.apache.commons.lang.Validate.notEmpty(Validate.java:340)
        at C2009051800.main(C2009051800.java:13)